1. Field of the Invention
The present invention relates to an ion implanter, and more particularly, to an apparatus for measuring a position of an ion beam profiler and a method of its use.
2. Description of the Related Art
Semiconductor manufacturing generally includes an ion implanting process that implants conductive impurities into a semiconductor wafer. This process uses an ion beam generated by an ion source. In a general ion implanter, impurities are ionized from an ion source, and these impurity ions are then accelerated to form an ion beam having a predetermined energy. The intensity and direction of the accelerated beam are controlled, so that the beam is implanted into the surface of a wafer. At this point, a conductive region corresponding to the energy of the ion beam may be formed in the wafer.
The energy of an ion contained in a beam is a crucial factor determining a travel depth within a semiconductor wafer before the ion is implanted into the wafer's semiconductor lattice. Recipes for a given integrated circuit device call for ion implanting using various ion species, energies, and doses. Therefore, when one parameter of an ion beam changes, other parameters in turn change. These changes often require a modification of the ion implanter. Also, preventive maintenance of the ion implanter is important to optimize transmission and transfer of the beam to the wafer.
Generally, during the set up or preventive maintenance of the ion implanter, an operator measures and examines the position of the center of a beam profiler to set parameters for a predetermined recipe in connection with a new beam profile of an ion implanter, which takes much time. For example, it often takes more than fifteen minutes for an experienced operator to set an ion implanter into an operable state. The ion implanter cannot perform an ion implanting process while the ion implanter is being set, so that equipment downtime occurs.
A general ion implanter includes an end station. The end station includes a platen for supporting a wafer, a tilt mechanism for tilt adjustments of the platen in X-axis and Y-axis directions, and a measurement system for measuring a parallel state and a direction of a beam. Also, the end station further includes a Faraday beam profiler located adjacent to the platen. The beam profiler allows a scanned ion beam to perform a translational motion parallel to the surface of the wafer. Therefore, uniformity of the scanned ion beam is determined by allowing the beam profiler to perform a translational motion across a plane of the wafer while monitoring a beam current.
As partly described above, a general ion implanter performs tilt mechanism correction and then senses an angle of an ion beam using a beam profiler and a Faraday cup to adjust the uniformity and direction of the ion beam. However, even when the sensed beam angle is compatible with a standard of a predetermined recipe, equipment tends to drift over time, causing errors that are detected when the beam angle is measured again during a subsequent process. Therefore, the position of the center of the beam profiler needs to be examined after the tilt mechanism correction.
For example, a high current or medium current ion implanter manufactured by Varian Semiconductor Equipment uses a jig set to measure and examine the center position of a beam profiler during set up (or prevention maintenance) after a tilt mechanism correction.
The jig set includes a body mounted in a slit provided to a profiler, a pendulum vertically falling to a platen's lower end that adjusts tilt of the platen through a thread coupled to a hole formed in one end of the body, and a ruler for contacting the platen to measure a distance between the thread and an outer periphery of the platen.
However, the above-described ion implanter performs platen tilt correction and then examines the center position of a profiler. At this point, because a chamber space of an end station is narrow, it is difficult to mount a jig set and check an exact position of the pendulum. Also, it is difficult to check center data during center examination. Also, since part of the jig set, namely a ruler, may directly contact the platen, there is a high possibility that scratches are generated on the surface of the platen. Also, since the outer periphery of the platen contacting the vertical surface of the ruler is a curved surface, it is difficult to measure exact center data.